mm/percpu-stats.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * mm/percpu-debug.c
   4  *
   5  * Copyright (C) 2017           Facebook Inc.
   6  * Copyright (C) 2017           Dennis Zhou <dennis@kernel.org>
   7  *
   8  * Prints statistics about the percpu allocator and backing chunks.
   9  */
  10 #include <linux/debugfs.h>
  11 #include <linux/list.h>
  12 #include <linux/percpu.h>
  13 #include <linux/seq_file.h>
  14 #include <linux/sort.h>
  15 #include <linux/vmalloc.h>
  16
  17 #include "percpu-internal.h"
  18
  19 #define P(X, Y) \
  20         seq_printf(m, "  %-20s: %12lld\n", X, (long long int)Y)
  21
  22 struct percpu_stats pcpu_stats;
  23 struct pcpu_alloc_info pcpu_stats_ai;
  24
  25 static int cmpint(const void *a, const void *b)
  26 {
  27         return *(int *)a - *(int *)b;
  28 }
  29
  30 /*
  31  * Iterates over all chunks to find the max nr_alloc entries.
  32  */
  33 static int find_max_nr_alloc(void)
  34 {
  35         struct pcpu_chunk *chunk;
  36         int slot, max_nr_alloc;
  37         enum pcpu_chunk_type type;
  38
  39         max_nr_alloc = 0;
  40         for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++)
  41                 for (slot = 0; slot < pcpu_nr_slots; slot++)
  42                         list_for_each_entry(chunk, &pcpu_chunk_list(type)[slot],
  43                                             list)
  44                                 max_nr_alloc = max(max_nr_alloc,
  45                                                    chunk->nr_alloc);
  46
  47         return max_nr_alloc;
  48 }
  49
  50 /*
  51  * Prints out chunk state. Fragmentation is considered between
  52  * the beginning of the chunk to the last allocation.
  53  *
  54  * All statistics are in bytes unless stated otherwise.
  55  */
  56 static void chunk_map_stats(struct seq_file *m, struct pcpu_chunk *chunk,
  57                             int *buffer)
  58 {
  59         struct pcpu_block_md *chunk_md = &chunk->chunk_md;
  60         int i, last_alloc, as_len, start, end;
  61         int *alloc_sizes, *p;
  62         /* statistics */
  63         int sum_frag = 0, max_frag = 0;
  64         int cur_min_alloc = 0, cur_med_alloc = 0, cur_max_alloc = 0;
  65
  66         alloc_sizes = buffer;
  67
  68         /*
  69          * find_last_bit returns the start value if nothing found.
  70          * Therefore, we must determine if it is a failure of find_last_bit
  71          * and set the appropriate value.
  72          */
  73         last_alloc = find_last_bit(chunk->alloc_map,
  74                                    pcpu_chunk_map_bits(chunk) -
  75                                    chunk->end_offset / PCPU_MIN_ALLOC_SIZE - 1);
  76         last_alloc = test_bit(last_alloc, chunk->alloc_map) ?
  77                      last_alloc + 1 : 0;
  78
  79         as_len = 0;
  80         start = chunk->start_offset / PCPU_MIN_ALLOC_SIZE;
  81
  82         /*
  83          * If a bit is set in the allocation map, the bound_map identifies
  84          * where the allocation ends.  If the allocation is not set, the
  85          * bound_map does not identify free areas as it is only kept accurate
  86          * on allocation, not free.
  87          *
  88          * Positive values are allocations and negative values are free
  89          * fragments.
  90          */
  91         while (start < last_alloc) {
  92                 if (test_bit(start, chunk->alloc_map)) {
  93                         end = find_next_bit(chunk->bound_map, last_alloc,
  94                                             start + 1);
  95                         alloc_sizes[as_len] = 1;
  96                 } else {
  97                         end = find_next_bit(chunk->alloc_map, last_alloc,
  98                                             start + 1);
  99                         alloc_sizes[as_len] = -1;
 100                 }
 101
 102                 alloc_sizes[as_len++] *= (end - start) * PCPU_MIN_ALLOC_SIZE;
 103
 104                 start = end;
 105         }
 106
 107         /*
 108          * The negative values are free fragments and thus sorting gives the
 109          * free fragments at the beginning in largest first order.
 110          */
 111         if (as_len > 0) {
 112                 sort(alloc_sizes, as_len, sizeof(int), cmpint, NULL);
 113
 114                 /* iterate through the unallocated fragments */
 115                 for (i = 0, p = alloc_sizes; *p < 0 && i < as_len; i++, p++) {
 116                         sum_frag -= *p;
 117                         max_frag = max(max_frag, -1 * (*p));
 118                 }
 119
 120                 cur_min_alloc = alloc_sizes[i];
 121                 cur_med_alloc = alloc_sizes[(i + as_len - 1) / 2];
 122                 cur_max_alloc = alloc_sizes[as_len - 1];
 123         }
 124
 125         P("nr_alloc", chunk->nr_alloc);
 126         P("max_alloc_size", chunk->max_alloc_size);
 127         P("empty_pop_pages", chunk->nr_empty_pop_pages);
 128         P("first_bit", chunk_md->first_free);
 129         P("free_bytes", chunk->free_bytes);
 130         P("contig_bytes", chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE);
 131         P("sum_frag", sum_frag);
 132         P("max_frag", max_frag);
 133         P("cur_min_alloc", cur_min_alloc);
 134         P("cur_med_alloc", cur_med_alloc);
 135         P("cur_max_alloc", cur_max_alloc);
 136 #ifdef CONFIG_MEMCG_KMEM
 137         P("memcg_aware", pcpu_is_memcg_chunk(pcpu_chunk_type(chunk)));
 138 #endif
 139         seq_putc(m, '\n');
 140 }
 141
 142 static int percpu_stats_show(struct seq_file *m, void *v)
 143 {
 144         struct pcpu_chunk *chunk;
 145         int slot, max_nr_alloc;
 146         int *buffer;
 147         enum pcpu_chunk_type type;
 148         int nr_empty_pop_pages;
 149
 150 alloc_buffer:
 151         spin_lock_irq(&pcpu_lock);
 152         max_nr_alloc = find_max_nr_alloc();
 153         spin_unlock_irq(&pcpu_lock);
 154
 155         /* there can be at most this many free and allocated fragments */
 156         buffer = vmalloc(array_size(sizeof(int), (2 * max_nr_alloc + 1)));
 157         if (!buffer)
 158                 return -ENOMEM;
 159
 160         spin_lock_irq(&pcpu_lock);
 161
 162         /* if the buffer allocated earlier is too small */
 163         if (max_nr_alloc < find_max_nr_alloc()) {
 164                 spin_unlock_irq(&pcpu_lock);
 165                 vfree(buffer);
 166                 goto alloc_buffer;
 167         }
 168
 169         nr_empty_pop_pages = 0;
 170         for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++)
 171                 nr_empty_pop_pages += pcpu_nr_empty_pop_pages[type];
 172
 173 #define PL(X)                                                           \
 174         seq_printf(m, "  %-20s: %12lld\n", #X, (long long int)pcpu_stats_ai.X)
 175
 176         seq_printf(m,
 177                         "Percpu Memory Statistics\n"
 178                         "Allocation Info:\n"
 179                         "----------------------------------------\n");
 180         PL(unit_size);
 181         PL(static_size);
 182         PL(reserved_size);
 183         PL(dyn_size);
 184         PL(atom_size);
 185         PL(alloc_size);
 186         seq_putc(m, '\n');
 187
 188 #undef PL
 189
 190 #define PU(X) \
 191         seq_printf(m, "  %-20s: %12llu\n", #X, (unsigned long long)pcpu_stats.X)
 192
 193         seq_printf(m,
 194                         "Global Stats:\n"
 195                         "----------------------------------------\n");
 196         PU(nr_alloc);
 197         PU(nr_dealloc);
 198         PU(nr_cur_alloc);
 199         PU(nr_max_alloc);
 200         PU(nr_chunks);
 201         PU(nr_max_chunks);
 202         PU(min_alloc_size);
 203         PU(max_alloc_size);
 204         P("empty_pop_pages", nr_empty_pop_pages);
 205         seq_putc(m, '\n');
 206
 207 #undef PU
 208
 209         seq_printf(m,
 210                         "Per Chunk Stats:\n"
 211                         "----------------------------------------\n");
 212
 213         if (pcpu_reserved_chunk) {
 214                 seq_puts(m, "Chunk: <- Reserved Chunk\n");
 215                 chunk_map_stats(m, pcpu_reserved_chunk, buffer);
 216         }
 217
 218         for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++) {
 219                 for (slot = 0; slot < pcpu_nr_slots; slot++) {
 220                         list_for_each_entry(chunk, &pcpu_chunk_list(type)[slot],
 221                                             list) {
 222                                 if (chunk == pcpu_first_chunk) {
 223                                         seq_puts(m, "Chunk: <- First Chunk\n");
 224                                         chunk_map_stats(m, chunk, buffer);
 225                                 } else {
 226                                         seq_puts(m, "Chunk:\n");
 227                                         chunk_map_stats(m, chunk, buffer);
 228                                 }
 229                         }
 230                 }
 231         }
 232
 233         spin_unlock_irq(&pcpu_lock);
 234
 235         vfree(buffer);
 236
 237         return 0;
 238 }
 239 DEFINE_SHOW_ATTRIBUTE(percpu_stats);
 240
 241 static int __init init_percpu_stats_debugfs(void)
 242 {
 243         debugfs_create_file("percpu_stats", 0444, NULL, NULL,
 244                         &percpu_stats_fops);
 245
 246         return 0;
 247 }
 248
 249 late_initcall(init_percpu_stats_debugfs);